Cellular iPad won’t connect to phone network
I have a cellular 10.2 iPad it works fine on WiFi but won’t connect to phone network
iPad Pro 10.5-inch, Wi-Fi, Cellular
Bearing in mind that the cellular option on iPads wifi+cellular models is used only when wifi is not available, and that the Sim card must be a "data only" card, contact your carrier and explain your problem.
Regards
Giulio